Comment 3 for bug 370559

this happens occasionally with my compiz + nvidia.
it might be triggered by opening/unminimizing windows while the other windows are "moved out" to show the desktop (but i haven't found a reliable way to reproduce this bug).
last time it happened, several of my windows became unreachable. after a short fight with keyboard shortcuts (alt+space move) and "expose" (which showed the windows but did not allow to activate it) the compiz finally crashed and the windows have returned to normal.